Primary fixation of mini slings: a comparative biomechanical study in vivo

The mini sling concept for stress urinary incontinence is an anatomical approach that involves placing a midurethral low-tension tape anchored to the obturator internus muscles bilaterally. They overcome the blind passage of long needles and all the related complications. There are many different devices available and because these are outpatient procedures, primary fixation plays an important role in the outcome. The objective is to evaluate the primary fixation of the various devices of attachment of the commercially available mini-slings through biomechanical tests.

A total of 45 Wistar rats were divided in 3 groups of 15 rats each. They underwent 5 subcutaneous implantation of different mini slings and one polipropilene mesh (control), as follows: TVT-Secur® (Gynecare, USA), Type 1 polypropylene mesh (control); Ophira Mini Sling System ® (Promedon, Argentina), Tissue Fixation System ® (TFS PTY, Australia), Zipper Sling ® and ″T device″ (Prosurg, USA). The abdominal wall was removed on bloc at different times after implant for biomechanical evaluation, which consisted in application of unidirectional force to the extremity of the fixation system or mesh, until it was completely removed from the tissue using a tension meter (Nexygen 3.0 Universal Testing Machine-LLOYD Instruments). The force was measured in Newtons (N).

There was significant difference in the resistance to extraction among the different fixation systems. At 7 days the Ophira Mini Sling System ® presented the best fixation and ″T dispositive″ the worst.

Ophira mini sling System ® presented the best primary fixation at 7°, 14° and 30° days. The impact of this feature in the clinical setting needs to be verified.